Evaluation of immunogenicity and protective efficacy against Mycobacterium tuberculosis infection elicited by recombinant Mycobacterium bovis BCG expressing human Interleukin-12p7 and Early Secretory Antigen Target-6 fusion protein
Early Secretory Antigen Target-6 (ESAT-6) protein of Mycobacterium tuberculosis is absent in Mycobacterium bovis Bacillus Calmette-Gu rin (BCG) and Mycobacterium microti and has been demonstrated to stimulate strong cell-mediated immunity. Interleukin-12 (IL-12) can play crucial roles in regulating IFN-? production and Th1 effectors production. In this study, we constructed three recombinant BCG (rBCG) vaccines that could express proteins of human IL-12p7 and/or ESAT-6 and evaluated their immunogenicity and protective efficacy in mice. Our experiments illustrated that the rBCG-IE (expressing a fusion protein of human IL-12p7 and ESAT-6) was capable of inducing stronger Th1 type cell-mediated immune responses than conventional BCG, or rBCG-I (expressing human IL-12p7), or rBCG-E (expressing ESAT-6). However, the results of protective experiments showed that rBCG-IE could only confer similar and even lower protective efficacy against M.tuberculosis H37Rv infection compared with BCG vaccine.